Patent GB-620872-A (GB)
Title: Improvements in variable speed power, transmission mechaní¡í¡
IPC: F16H37/00
Filed: 1947-01-28
Abstract: 620,872. Servomotor-control systems. FORD MOTOR CO., Ltd. Jan. 28, 1947, No. 2661. Convention date, Feb. 23, 1946. [Class 135] [Also in Groups XXIV and XXXIV] In a three-speed epicyclic gear having governorcontrolled hydraulic clutches giving automatic ratio change, an additional hydraulically - actuated gear is provided to produce the normal high or intermediate speeds and speeds between high and intermediate, and intermediate and low. The automatic change-speed gear of Specification 615,175, [Group XXIV], is modified by the addition of a second fluid pressure pump and two speed planetary gear, located between the fluid coupling and the threespeed and reverse planetary gearing, and the addition of accelerator and manually-controlled valves to provide two additional kick-down ratios between the normal ratios for emergency conditions and means for shifting to a lower speed and preventing over-running so that the engine can be used as a brake. The additional pump unit 41 is driven at engine speed from the impeller casing 15 of the fluid coupling through a sleeve 74 surrounding the main shaft 13, and supplies pressure fluid, at a pressure determined by the valve 79, to the conduit 43 communicating with the delivery chamber of the pump 42 driven by the driven shaft 14 of the system. A relief valve 46 modifies the delivery pressure of the pump 42 according to the rate of a spring 47 and to the engine manifold suction by a bellows 48 so that the fluid pressure in the chamber 44 is proportional to the engine torque. A ball-valve is incorporated in the delivery side of the pump 41 to prevent the relief valve 79 destroying the higher pressure generated by the pump 42. The chamber 44 communicates with the bore of a rotary distributing valve 51 operatively connected to the accelerator pedal 52, this valve throughout its normal travel connecting the chamber 44 with the conduit 53. The conduits 43, 53, supply fluid under pressure for actuating the intermediate and high-speed clutches 24, 28. respectively, under the control of the governorcontrolled slide valve 56 driven by the main shaft 13. A second rotary valve 58 is manually operated from a control lever on the steering column to supply pressure selectively to brakes 67, 65, 66 for forward, reverse and downhill braking. Two-speed planetary gear.-The two-speed gear 22, Fig. 4, comprises an annulus gear 75 integral with the engine driven sleeve 74, having a splined periphery in driving connection with the clutch plates 95 co-operable with similar plates 94 splined to a flanged disc 92 rigid with a sun-gear 88. The planet carrier 84 is splined to the hub of intermediate speed clutch member 86 and carrier journalled thereon the sun-gear 88. The clutch disc 92 is formed with six cylinders 96, within which are pistons 97 arranged to exert force through the actuating ring 98 upon the clutch plates 94, 95, when fluid is admitted from the conduit 43 through passages 105, 101, 100, groove 108 in the clutch valve disc 106 and passage 99 in the clutch disc 92. The valve 106 is formed with an axially-extending flange 107, co-operating with a brake band 111, and is normally retained in a predetermined angular relationship with the groove 108 aligned with the passages 100, 99, by balls located in aligned conical recesses in the valve disc 106 and a clutch ring 119, the disc 106 and the ring 119 being urged together by spring means. Application of the brake 111 retards the valve disc 106 and the sun-gear 88 and causes relative rotation of the valve disc and clutch disc to cut off the fluid supply to the cylinders 96 and vents them to atmosphere through passages 109, 110, resulting in the release of the clutch and the transmission of the drive from the coupling 15 to the intermediate speed clutch member at a reduced ratio. Forward and reverse brakes.-The forward and reverse brakes 38, 68, co-acting with the one-way clutch 39 and the clutch carrier 23, are similar in construction and comprise a pair of axially-spaced bands 141, 142 having 2¥ and 2 convolutions respectively, the ends of the bands being anchored at diametricallyopposite points to balance torque reaction forces by studs 144, 147 having teeth 145 engaging similar teeth 146 on the bands. The bands are actuated by fluid pressure from the manual valve 58 on the piston 148 which transmits thrust to an equalizing lever 151 to studs 153 carried by the free ends of the brake bands. The bands may be bi-metallic, such as copper plated steel bands, their natural resiliency providing the necessary spring off. Hydraulic system.-Pressure fluid is pumped by the front engine driven pump 41 to the conduit 43 and thence to the rear output shaft driven pump 42 where the two pump outputs are combined in the chamber 44 and proportioned to engine torque by the bellows control on the relief valve 46. From the chamber 44, pipe 49 leads fluid to the central bore of the rotary, accelerator controlled valve 51. When the valve 51 is in the idling position the pipe 61 leading to the manually controlled valve 58 is connected to atmosphere, thus venting the brakes 65, 66, 67 and preventing idling drag due to the hydraulic coupling. Initial movement of the accelerator rotates the valve 51 to connect the pipe 61 to the pressure supply and thus pressurize the central bore 168 of the valve 58 which by its rotation in an anti-clockwise direction establishes communication with the conduits 62, 63, 64 leading to the reverse, downhill brake, and forward speed brakes respectively. Simultaneously with the pressurizing of the valve 58, the valve 51 connects its central bore with the conduit 53 leading, through the centrifugal valve 56, to the high-speed clutch 28, thus after the initial movement of the accelerator and with the valve 58 set as shown in Fig. 16 in the forward position, gear changes are made by the governor 57 as described in the earlier Specification. For reverse, the valve 58 is rotated manually to cut off pressure to the brake 67 and to pressurize the brake 65, the clutches 24, 28 being disengaged, thus the drive passing through the coupling 16 to the planetary gear 36, 33, 34, 37 and to the output shaft 14. For the first kick-down shift the accelerator is depressed to 90 to 100 per cent full travel, which rotates the valve 51 to pressurize the brake 117 of the planetary two-speed gear 22 through the conduits 189, 118, at the same time providing additional pressure to the relief valve 46 through the conduit 191 to increase the fluid pressure in the clutches 24, 28 having regard to the increased torque transmitted by them when the underdrive 22 is employed. Further movement of the accelerator through 100 to 110 per cent travel rotates the valve 51 still further to open the conduit 53 supplying the high-speed clutch 28 to atmosphere, thus providing a double reduction by use of the planetary gear 22 and intermediate gear. For downhill operation, in which the second kickdown ratio is employed to give an engine braking effect, the manual valve 58 is rotated to connect the conduits 63, 64 to the pressure supply, thus energizing the down-hill brake 66 and the forward speed brake 67, simultaneously, movement of the lever 195, Fig. 1, to rotate the valve 58 causes rotation of the valve 51 through the cams 207, 202, a lever rigid with the sector 198 and pinion 197 on the spindle of the valve 51, the accelerator control so this valve having a lost-motion connection through a bell-crank 204 pivoted thereon. This rotation of the valve 51 produces the same effect as 100 to 110 per cent accelerator travel to engage the lower speed of the planetary unit 22 and to disengage the high-speed clutch 28, thus producing second kick-down speed with the planet carrier 27 locked against both directions of rotation.